Un-combusted diesel fuel, including ultra-low sulfur diesel (ULSD), has a strong odor. The odor often associated with diesel is unpleasant and may deter customers from purchasing diesel vehicles. In particular, the diesel fuel, when spilled, especially on one's hands or clothing, may have a prolonged bad odor. Also diesel fuel stored in equipment contained in garages, basements, sheds, or even houses can emit an odor that may make it undesirable to store the equipment or fuel indoors.
Several factors lead to diesel fuel odor. Eliminating only some of the factors can result in a diesel fuel that still has an unacceptable odor. Understanding and controlling most or all the factors is necessary to achieve a fuel that has a truly low odor level or no odor. Another important consideration is that when the odor causing components are eliminated from the prospective fuel it may no longer meet all the required specifications for the fuel. Only by careful balancing of the factors can a fuel be produced that both has low odor and meets diesel fuel specifications.
Additionally, emissions, especially NOx emissions, from vehicles utilizing diesel are also relatively high. The current approach in reducing NOx to levels that meet governmental environmental regulations is to use exhaust aftertreatment systems (such as Selective Catalyst Reduction Systems or NOx traps) that convert engine-out NOx to less harmful species such as N2. However, these systems are not always the best solution because they may (1) be costly, (2) add to the weight of the vehicle, (3) require addition of chemicals such as urea, and (4) hurt fuel economy due to the added weight and the need to burn additional fuel to regenerate the NOx conversion components. Use of the premium, odorless diesel product of the present invention will produce less engine-out NOx, thus enabling less frequent regenerations, and/or a reduction in size or elimination of the aftertreatment system. Further, older vehicles which do not have extensive aftertreatment equipment should have lower emissions with this premium, odorless diesel product.
It has been discovered that some key factors in reducing or eliminating diesel fuel odor are adjusting the aromatic content, adjusting the amounts of volatile and low-boiling point compounds, and controlling the amount of sulfur and other heteroatoms in the diesel fuel. It has also been discovered that this low/no odor diesel fuel, when employed in certain engine environments, results in low NOx emissions.